Finding days in previous month


 
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# 1  
Data Finding days in previous month

Code:
 
#!/bin/ksh
day=1
month=1
year=2012
if [ $day -eq 1 ] then
[
if [$month -eq 1 ||  $month -eq 5 || $month -eq 7 ||  $month -eq 9 || $month -eq 11]
then
 prevmonth=31
elif [$month -eq 2 ||  $month -eq 4 || $month -eq 6 ||  $month -eq 8 || $month -eq 10 || $month -eq 12]
then
 prevmonth=30
elif [$month -eq 3]
then
[
if [year%100 -eq 0 && year%400 -eq 0]
then prevmonth=29
elif [year%100 -ne 0 && year%4 -eq 0]
then prevmonth=29
else
prevmonth=28
fi
]
]
if[$day -eq 1 && $month -eq 1]
then
year=$($year-1)
fi
echo $prevmonth

I am trying the code above and i am getting the following error.

Code:
 
/pain.ksh[5]: syntax error at line 27 :

Help needed to resolve the error.

Last edited by vagar11; 08-14-2012 at 07:43 AM.. Reason: Changed QUOTE tags to CODE tags
# 2  
Code:
year=$(( $year - 1 ))

# 3  
getting this error now
Quote:
./pain.ksh[5]: syntax error at line 5 : `if' unmatched
---------- Post updated at 04:53 PM ---------- Previous update was at 04:14 PM ----------

Made some changes in the code :

Quote:
#!/bin/ksh
day=1
month=1
year=2012
if [ $day -eq 1 ]
then
if [ $month -eq 1 -o $month -eq 5 -o $month -eq 7 -o $month -eq 9 -o $month -eq 11 ]
then
prevmonth=31
elif [ $month -eq 2 -o $month -eq 4 -o $month -eq 6 -o $month -eq 8 -o $month -eq 10 -o $month -eq 12 ]
then
prevmonth=30
elif [ $month -eq 3 ]
then
if [ year%100 -eq 0 && year%400 -eq 0 ]
then prevmonth=29
elif [ year%100 -ne 0 && year%4 -eq 0 ]
then prevmonth=29
else
prevmonth=28
fi
fi
fi
if [ $day -eq 1 && $month -eq 1 ] then
year=$(($year-1))
fi
echo $prevmonth
getting the error below
Quote:
./pain.ksh[24]: syntax error at line 27 : `fi' unexpected
please help !!

---------- Post updated at 05:15 PM ---------- Previous update was at 04:53 PM ----------

problem resolved.
took then in the next line.

If anybody wants i can post the final code here for finding previous day in month.
# 4  
I took your original posting, reformatted it so I could follow what was going on, fixed the syntax errors, and fixed some logic bugs. There are comments in-line showing what I changed and why.
Code:
#!/bin/ksh
# indentation added to make it easier to see the logic
day=1 # not needed, it is always set below to the last day of the previous month
# delete this duplicate line: #!/bin/ksh
# delete this duplicate line: day=1
month=1
year=2012
if [ $day -eq 1 ] # added a missing <semicolon> or <newline> here
then { # [ change to {
        if [[ $month -eq 1 || $month -eq 2 || $month -eq 4 || $month -eq 6 || $month -eq 8 || $month -eq 9 || $month -eq 11 ]]
        # <space> added after [ and before ] on above line
        # and [ and ] changed to [[ and ]], respectively, and
        # 31 day months changed from 12, 4, 6, 8, & 10 to 12, 1, 3, 5, 7, 8, & 10
        then prevmonth=31
        elif [[ $month -eq 5 || $month -eq 7 || $month -eq 10 || $month -eq 12 ]]
        # <space> added after [ and before ] on above line
        # and [ and ] changed to [[ and ]], respectively, and
        # 30 day months changed from 1, 3, 5, 7, 9, & 11 to 4, 6, 9, & 11
        then prevmonth=30
        elif [ $month -eq 3 ]  # this line could just be else
        # <space> added after [ and before ] on above line
        then {  if [[ $((year%100)) -eq 0 && $((year%400)) -eq 0 ]]
                # <space> added after [ and before ] on above line
                # and [ and ] changed to [[ and ]], respectively
                # and $((...)) added around both year%... calculations
                # and then [ changed to then {
                then prevmonth=29
                elif [[ $((year%100)) -ne 0 && $((year%4)) -eq 0 ]]
                # <space> added after [ and before ] on above line
                # and [ and ] changed to [[ and ]], respectively
                # and $((...)) added around both year%... calculations
                then prevmonth=29
                else prevmonth=28
                fi
        } # ] changed to }
        fi #this was missing
} # ] changed to }
fi #this was missing
if [[ $day -eq 1 && $month -eq 1 ]] # <space> added after if
# <space> added after [ and before ] on above line
# and [ and ] changed to [[ and ]], respectively
then    year=$(($year-1))
        # $(...) change to $((...))
fi
echo $prevmonth

I hope this helps.
# 5  
A possible alternative ...

Subtract one from the month, m. If m equals 0, set m to 12 and subtract 1 from the year, y.
Code:
cal m y | tr -s ' \t' '\n\n' | tail -n1

cal's output isn't standardized, but that may work across different systems.

Regards,
Alister
 

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